The invention relates to a plunging assembly for a driveshaft, especially for being used in the driveline of a motor vehicle. The driveshaft comprises two joints which permit articulation angles only and which are connected to one another by a connecting shaft. The plunging assembly of the connecting shaft serves to compensate for any changes in the distance between the articulation centers of the joints, which changes result from positional changes of the joints.
DE 44 19 373 C2 describes such a driveshaft wherein one of the two constant velocity joints is provided with a plunging journal which is produced so as to be integral with the constant velocity joint and which, in its outer face, comprises a plurality of circumferentially distributed first running grooves extending parallel to the longitudinal axis. The connecting shaft comprises a corresponding plunging portion whose cross-section has the shape of a corrugated tube into which the plunging journal enters in an axially movable way. In the bore of the plunging portion, there are provided second running grooves which are arranged opposite the first running grooves of the plunging journal and extend parallel to the longitudinal axis. The first and second running grooves which, together form pairs, accommodate rolling contact members which are arranged one behind the other in a running groove. At the end of the plunging portion there is provided a securing ring which, when the plunging journal moves, delimits the movement of the rolling contact members in the pulling-out direction. An insert arranged in the bore of the plunging portion delimits the plunging movement of the plunging journal relative to the plunging portion in the moving-in direction. However, the design as described does not permit the outer part to cover plunging paths relative to the inner part which are longer than those normally occurring in operation. Furthermore, in the unmounted condition of the driveshaft, the plunging journal is not secured against unintentionally falling out of the plunging portion.
U.S. Pat. No. 3,186,189 shows a plunging part for a driveshaft, wherein a plunging journal is connected to a constant velocity joint and arranged inside a bore of a plunging portion of the connecting shaft. The plunging journal and the plunging portion each comprise opposed running grooves in which rolling contact members carry out rolling movements. In the moving-in direction, the movement of the plunging journal relative to the plunging portion is delimited by a plug which is positioned in the bore of the plunging portion and abuts against the plunging journal. In the pulling-out direction, the movement of the plunging journal is delimited by an annular member at the plunging portion, against which annular member there abut shoulders of the regions between two adjoining running grooves. To prevent the balls from unintentionally leaving the running grooves of the plunging journal when the plunging journal has assumed one of its end positions, securing rings are provided at both ends of the running grooves.
DE 197 39 934 A1 describes an example of a rolling contact assembly wherein the inner part of the plunging assembly is inserted into one of the joint parts of the constant velocity joint. The outer part of the constant velocity joint is firmly connected to the intermediate shaft and comprises a through-bore provided with outer running grooves which are circumferentially distributed around a longitudinal axis and which extend parallel relative to the latter. The inner part plunges into the outer part, with the outer face of the inner part having inner running grooves which are circumferentially distributed in accordance with the outer running grooves. In each of the opposed pairs of outer running grooves and inner running grooves, there is arranged a plurality of balls one behind the other along the longitudinal axis and held by a cage. The plunging movement of the plunging unit, composed of the cage and the balls, relative to the outer part is delimited by stops. When the plunging unit is stationary, the inner part can be pulled further out of the outer part than necessary under operational conditions. In the process, the balls of the plunging unit slide in the inner running grooves of the inner part. The moving-in movement of the inner part relative to the outer part is delimited in that the balls facing the intermediate shaft stop against the run-out faces of the outer running grooves of the outer part, with the inner part coming into contact with the intermediate shaft.
Accordingly, it is an object of the present invention to provide an improved plunging assembly. Another object is to provide a plunging assembly for a driveshaft having a simple design and which delimits the rolling and a sliding movement of the inner part relative to the outer part during the moving-in and moving-out processes without there being any risk of the balls of the cage being jammed in between the outer part and inner part, thus blocking the plunging unit.
In accordance with the invention, the foregoing and other objectives and advantages are achieved by a plunging assembly for a driveshaft which comprises an outer part which is arranged so as to be centered on a longitudinal axis and which, furthermore, comprises a bore which is arranged so as to be centered on the longitudinal axis and which is provided with circumferentially distributed outer running grooves which extend parallel to the longitudinal axis. The plunging assembly also includes an inner part whose outer face is provided with inner running grooves which extend parallel to the longitudinal axis and which are positioned opposite the outer running grooves. A plunging unit is also included comprising a cage which is sleeve-shaped, which is arranged coaxially around the inner part, and is positioned in the bore so as to be displaceable relative to the outer part and inner part and which, furthermore, in accordance with the pairs of opposed outer running grooves and inner running grooves, comprises apertures, as well as balls which are held in the apertures and engage the outer running grooves and the inner running grooves. Means for delimiting the path which can be covered by the inner part relative to the outer part during the moving-in motion are also provided in the form of a first moving-in stop and a second moving-in stop. Means for delimiting the path which can be covered by the inner part relative to the outer part during the moving-out motion are also provided in the form of a first moving-out stop and a second moving-out stop. The first moving-in stop and the first moving-out stop delimit the effective length of the outer running grooves with respect to the path which can be covered by the plunging unit relative to the outer part. Furthermore, the second moving-in stop and the second moving-out stop delimit the effective length of the inner running grooves with respect to the path which can be covered by the plunging unit relative to the inner part, with the length of the inner running grooves deviating from the length of the outer running grooves.
One advantage of the present invention is that the change in the length of the driveshaft occurring under operational conditions can be achieved by rolling displacement of the balls of the plunging unit. The rolling displacement path is the path which can be covered by the inner part relative to, and into, the outer part, starting from a first position wherein the plunging unit rests against a first moving-out stop as far as a position wherein the plunging unit rests against the first moving-in stop. Due to the kinematic conditions, the rolling displacement path is twice as long as the displacement path of the plunging unit between the stops. The effective length of the outer running grooves is therefore the set path covered by the plunging unit between the stops, and of the length of the plunging unit between its parts touching the two stops. If an additional set path is required, the length of the inner running grooves has to deviate from the length of the outer running grooves. If the path to be covered by the plunging unit relative to the inner part is greater than that to be covered relative to the outer part, the setting movement takes place on the inner part. On the other hand, the setting movement of the plunging unit takes place on the outer part, if the path to be covered by the plunging unit relative to the inner part is smaller than that to be covered relative to the outer part.
This design measure ensures that identical types of driveshaft can be used for certain applications, so that, first, the insertion depth of the inner part in the outer part is slidingly set, and subsequently, within the limits of the proposed path as set for the plunging unit, there takes place a rolling displacement between the outer part and the inner part. The path set additionally can also be used, for example when assembling or dismantling a driveshaft, for moving the driveshaft into a shortened position which goes beyond the standard operating positions.
By delimiting the path to be covered by the plunging unit relative to the inner part by way of a second moving-in stop and a second moving-out stop, the inner part, in the course of dismantling, is prevented from completely moving out of the outer part or from moving too far into the outer part. In particular by delimiting the path to be covered by the plunging unit relative to the inner part and outer part, the balls are prevented from reaching the region of the running groove ends where they could be jammed in between the inner part and outer part, in which case the plunging unit would be blocked.
According to another embodiment of the invention, the first moving-in stop of the plunging unit is formed by stop faces delimiting the end of the outer running grooves of the outer part, with the cage, in the moved-in condition of the plunging unit, being supported thereon in such a way that a distance exists between the stop faces of the outer running grooves and the directly adjoining balls. The cage, by way of its end face, stops against the stop faces of the outer part. In this embodiment, the balls of the plunging unit are prevented from stopping against the stop faces of the outer running grooves and from being jammed in between these and the inner running grooves of the inner part. It is also conceivable for the cage, at its end, to comprise at least one radial projection acting as a stop against the track end.
A further embodiment is provided wherein the first moving-out stop comprises a securing ring which can be firmly inserted into the bore of the outer part and which serves as a stop for the cage or the balls of the plunging unit. This embodiment allows the inner part and the plunging unit to be easily assembled with the outer part. After the inner part and the plunging unit have been slid into the outer part, the securing ring connected to the outer part near the bore aperture of same prevents the plunging unit and the inner part from sliding out of the outer part. For dismantling purposes, the securing ring is released from the outer part, so that the inner part, together with the plunging unit, can be pulled out of the outer part.
The first moving-out stop can also comprise an annular element which is arranged at that end of the outer part into which the inner part is inserted. Furthermore, the annular element comprises a circular-ring-shaped stop face which points radially inwardly. The annular element is preferably produced by a non-chip forming machining method, such as by rolling. If the annular element is produced by rolling, it can be directly formed on to the outer part, so that the circular-ring-shaped stop face is formed while the annular element is formed on. In addition, the annular element can comprise a seat for a convoluted boot.
In a further embodiment, the second moving-out stop of the plunging assembly comprises a securing ring which is connected to the inner part end located in the outer part, which also serves as a stop for the cage or the balls of the plunging unit and which is arranged in front of the end of the inner running grooves. The second moving-out stop delimits the sliding displacement path of the plunging unit relative to the inner part. The inner part is thus prevented from moving out of the outer part during dismantling in an uncontrolled way.
A further embodiment provides that the second moving-in stop comprises a securing ring which is secured at that end of the inner running grooves of the inner part which emerges from the outer part, which, furthermore, serves as a stop for the cage or the balls of the plunging unit and which is arranged in front of the end of the inner running grooves. The second moving-in stop delimits the sliding displacement path of the inner part relative to the plunging unit and to the outer part. During the moving-in movement of the inner part, the securing ring stops against the cage of the plunging unit, thus preventing the inner part from slidingly moving into the outer part and also preventing the balls from being jammed in between the running-out faces of the inner grooves of the inner part and the outer grooves of the outer part.
According to a further embodiment of the invention, there are provided means, in the form of a plate metal cup, for sealing the bore of the outer part, the means preventing the lubricant from flowing out of the plunging unit through the bore of the outer part when the driveshaft is in operation. At the plunging assembly end facing the joint, there is provided a convoluted boot which seals the aperture between the outer part and the joint and the inner part respectively.
A particularly preferred embodiment of the invention provides that the delimited path to be covered by the plunging unit relative to the inner part is longer than the delimited path to be covered by the plunging unit relative to the outer part. The advantage of this design measure is that in the case of a maximum rolling and sliding displacement path, the length of the outer running grooves of the outer part is minimal.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.